At this point the best you could do is have a high queue-length number. Setting the overflow-action to DISCARD you will definitely lose messages. Setting to BLOCK it will block synchronously until there is room on the queue to add the message.

The queue-length is the number of messages to store before it blocks or discards messages. If you set the queue-length to 100 then it will store up to 100 messages before it either blocks or discards messages.